1. Field of the Invention
The present invention relates to a seal structure for a combustor liner. More specifically, the present invention relates to a seal structure suitable for a combustor liner included in a gas turbine used in an aircraft engine, etc.
2. Description of the Related Art
The development of ceramic materials, such as ceramic matrix composites (CMCs) superior in heat resistance to metallic materials, has advanced in recent years, and studies have been made to apply ceramic materials to forming combustor liners. A conventional combustor liner formed of a metallic material has a low heat resistance and hence it is difficult to reduce cooling air greatly. A combustor liner formed of a ceramic material having a high heat resistance enables the reduction of cooling air and the improvement of thermal efficiency, and the reduction of emission of nitrogen oxides by using the surplus cooling air for lean-burn combustion.
Generally, ceramic materials are brittle and have coefficients of linear thermal expansion smaller than those of metallic materials. Therefore, when a combustor provided with a ceramic combustor liner operates for combustion, the difference in thermal expansion between the ceramic combustor liner and metallic parts combined with the ceramic combustor liner is large. Thus, seal structures for sealing a gap between the ceramic combustor liner and a neighboring metallic structure must be capable of absorbing the difference in thermal expansion between the combustor liner and the neighboring structure.
As shown in FIGS. 9A and 9B, a conventional combustor liner seal structure disclosed in Japanese Pat. No. 2852110 includes a plate spring 103 which seals gaps between a premixer 101 and a liner 102, and absorbs the displacement of the premixer 101 and the liner 102 relative to each other by the elastic deformation of the plate spring 103. A conventional seal structure disclosed in JP-A No. 285284/1996 includes a plate spring which seals gaps between a liner and a transition piece.
Many conventional combustor liner seal structures utilize the elastic property of a plate spring. Those conventional combustor liner seal structures, however, need to use a plate spring having a small spring constant or a long plate spring in order that a high stress may not be induced in the plate spring due to the difference in thermal expansion between the combustor liner and the associated structure, and the liner may not be excessively loaded.
The difference in thermal expansion between a combustor liner formed of a ceramic material and a structure associated with the combustor liner is very large, and hence a considerably long plate spring is needed to seal gaps between the combustor liner and the associated structure. Such a long plate spring needs a large space for installation.
The necessity of such a large space for installation is a serious disadvantage in aircraft designing in which weight and space reduction is one of the most important subjects. Since a long plate spring is subject to large thermal deformation, the long plate spring has difficulty in maintaining a stable sealing function. This problem will become more serious when a liner of CMC is exposed to higher temperature than that for a liner of metal.
The present invention has been made in view of the foregoing problems in the related art and it is an object of the present invention to provide a seal structure for sealing a gap between a combustor liner and a neighboring structure, capable of absorbing difference in thermal expansion between the combustor liner and a neighboring structure and of satisfactorily sealing the gap between the combustor liner and the neighboring structure.
According to the first aspect of the present invention, a seal structure for sealing a gap between a combustor liner and a neighboring structure adjacent to the combustor liner, comprises: an annular sealing member mounted on the neighboring structure so as to be in contact with an annular outer surface of the combustor liner to seal the gap between the combustor liner and the neighboring structure, the annular sealing member including a plurality of sealing segments which are arranged in an annular form as a whole.
Preferably, the seal structure further comprises a pressing unit having an annular elastic member to press the sealing segments against the outer surface of the combustor liner.
Preferably, the annular elastic member has a break.
Preferably, each of the sealing segments is supported so as to be movable in a predetermined range.
Preferably, each of the sealing segments is movable in a radial direction.
Preferably, the combustor liner includes an annular outer liner and an annular inner liner which are configured to define an annular combustion chamber together with an annular dome, and the seal structure includes a pair of the annular sealing members which are disposed to seal a gap between the annular outer liner and a neighboring structure adjacent to the annular outer liner and a gap between the annular inner liner and a neighboring structure adjacent to the annular inner liner, respectively.
Preferably, the combustor liner is made of a ceramic material.
According to the second aspect of the present invention, an annular combustor comprises: a combustor liner configured to define an annular combustion chamber, the combustor liner having an annular outer surface; a neighboring structure adjacent to the combustor liner; a seal structure for sealing a gap between the combustor liner and the neighboring structure, the seal structure comprising: an annular sealing member mounted on the neighboring structure so as to be in contact with the annular outer surface of the combustor liner to seal the gap between the combustor liner and the neighboring structure, the annular sealing member including a plurality of sealing segments which are arranged in an annular form as a whole.
Preferably, the seal structure further comprises a pressing unit having an annular elastic member to press the sealing segments against the outer surface of the combustor liner.
Preferably, the annular elastic member has a break.
Preferably, each of the sealing segments is supported so as to be movable in a predetermined range.
Preferably, each of the sealing segments is movable in a radial direction.
Preferably, the combustor liner includes an annular outer liner and an annular inner liner which are configured to define the annular combustion chamber together with an annular dome, and the seal structure includes a pair of the annular sealing members which are disposed to seal a gap between the annular outer liner and a neighboring structure adjacent to the annular outer liner and a gap between the annular inner liner and a neighboring structure adjacent to the annular inner liner, respectively.
Preferably, the combustor liner is made of a ceramic material.
The seal structure of the present invention is capable of satisfactorily sealing the gap between the combustor liner and the neighboring structure without placing an excessive load on the combustor liner even if the difference in thermal expansion between the combustor liner and the neighboring structure is large.